Many products, such as granular and liquid materials, are shipped and stored in large bulk bags adapted to hold as much as a ton or more of material. The use of bags for this purpose has become popular because the bags can be shipped from the manufacturer to the material shipper in a generally flat condition and, if properly designed, when empty can be returned by the user to the shipper in the same generally flat condition for reuse. Commercially successful examples of such bags are disclosed and claimed in U.S. Pat. Nos. 4,518,106; 4,596,040; 4,781,472; 4,781,473; 4,781,475; 4,790,029; and 4,817,824; 5,087,235; 5,104,236; 5,127,893; 5,328,268; 5,358,335; and 5,142,804, all assigned to Custom Packaging Systems, Inc., assignee of record herein, and incorporated herein by reference.
In addition, it is desirable, as set forth in the above identified patents, to provide the bulk bags with loose and attachable leak proof liners made of liquid and moisture impervious inexpensive plastic sheet material which form-fit within the container bag without pleats or folds in the liner when filled so that no abnormal stress is put on the liner, the bulk bags can be filled to maximum capacity, and no valuable product is trapped in the pleats or folds of the liner. Such liners eliminate dusting or splashing and container odors during filling or discharging cycles in use of the bags. Such liners are constructed for insertion into any style bulk bag and are easily filled. The liners do not elongate out of the bottom of the bulk bag during discharge due to their attachment features to the exterior bag, such as tape-tab and sewing techniques which holds the liner permanently in place, or a tape-tab and tied feature which allows removal of a used liner and a new liner to be inserted and tied into the bag, thereby allowing reuse of the outer bag. Use of such liners in the outer bulk bags saves on cleaning, storage of waste, and container replacement costs. Additionally, liners constructed in accordance with the aforementioned patent disclosures may be quickly inserted into the outer woven bag and inflated in seconds to correctly fit the bag container.
The liners can be provided in a variety of single or multi-ply plastic sheet materials to prevent problems related to corrosion, oxygen, moisture, conductivity, high temperature, and static electricity. Additionally, such bulk liquid bag liners can be provided with rigid inlet and/or outlet spout fitments to control liquid product inflow and outflow and easy closure.
Despite the many advantageous characteristics and features of the aforementioned patented bulk bag and liner constructions, there remains a need to improve the attachment connection of the rigid spouts as used in inlet and discharge liner fitments to the liner in a secure, liquid-tight and leak proof manner. Typically such rigid spouts are commercially available as separate components and injection molded of suitable plastic materials. The cylindrical tube barrel that defines the main conduit of the spout is normally provided with an integral outwardly extending flange base that encircles the barrel and is adapted for attachment to the single or multi-ply plastic material of the liner, which in turn is suitably apertured to receive the spout therethrough. Typically, such rigid spout fitments are referred to in the trade as a "fill flange" and "discharge flange" because of their characteristic mounting flange base portion, which in turn is often referred to as the "flange base".
Such commercially available fill and discharge flanges may be of the "open flange" type, which means that the spout barrel may be provided with an externally or internally threaded portion adapted to threadably receive a removable closure plug or cap that is accessible externally of the liner to open and close the flange. Another type of such flange is the "closed flange" type that is initially manufactured in closed condition by attachment thereto a sheet of sealing material adhesively attached, as by a heat seal weld, to the flange base so that the closed flange can only be opened by piercing this seal piece, to rupture it and thereby open the flange after external coupling connections have been made to an external fill or discharge hose or conduit.
Typically, in manufacture of prior liner constructions employing such fill and discharge flanges, one or more plies of thermoplastic liner sheet material were heat sealed to the thermoplastic material of the flange base by use of a heat sealing head fixture of the either the induction heater or ultrasonic welding type, such as that disclosed in U.S. Pat. No. 3,916,148 and referenced in the above-noted U.S. Pat. No. 5,087,235, both incorporated herein by reference. This created a single annular zone of a fused ring of heat welded fused plastic material that was formed between the liner ply and the base surface encircling the flange barrel. In the case of closed flange, either simultaneously or successively, one or more barrier seal pieces thermoplastic sheet material were often heat sealed to the opposite side of the flange base to form an interior seal membrane, the fusion welding zone being aligned or registered with that of the ply or plies welded to the opposite side of the flange base.
It has been found that this prior spout-to-liner attachment construction, although generally satisfactory under most usage conditions, in some instances has not provided a leak-proof spout fitment system. Such fitments are subject to occasional development of "leakers" due to "over cooked" seals, resulting when the heat weld joint is stressed in tension, in a tearing action along a seal edge, thereby causing leaking next to the outside of the seal edge during bag transit, or even before filling the bag liner with any liquid at all. It will be understood that particularly in the case of discharge fitments for bulk liquid bag liners, that the same are subjected to severe hydraulic stresses from the weight of the filled bag liquid contents while in transit, and to additional shock stresses from bumping or mishandling while being moved from storage to the discharge station as by forklifts, overhead cranes and the like. In addition, in the prior manufacture of such spout-to-liner constructions several separate manufacturing steps are often required that involve rehandling of the product and therefore increased possibility of processing errors and defects resulting from successive tolerance stack-ups.